Cr-Mn

Cr - Mn Technical Publications

200. The Effect of Sintering Conditions and Composition on the Mechanical Property Response of Cr Containing PM Steels The desire for advanced ferrous PM materials has led to the development of alloys that more closely simulate wrought steel compositions. Traditional wrought steel alloying elements, such as Cr, are used to improve mechanical properties, hardenability and are cost effective. Chromium has historically been avoided in PM due to oxygen related issues, but newer PM alloy systems now contain this element. While providing good mechanical properties and overall product cost, proper sintering of these alloys is the critical challenge. This paper presents the role of sintering and composition on the mechanical properties and microstructure of a chromium containing PM steel.

196. Sintering of Powder Premixes - A Brief Overview Advances in the understanding of the sintering of powder premixes have contributed significantly to the growth of the ferrous powder metallurgy industry. This includes sintering both in the solid state and in the presence of a liquid phase. In this article, the sintering of iron powder premixes containing: 1) graphite; 2) nickel and graphite; 3) copper and graphite; 4) Phosphorus as ferrophosphorus; and, 5) boron as ferroboron are discussed. The evolution of microstructure and mechanical properties are discussed as well.

193. Chromium Steels for High Performance PM Applications Chromium steels have long dominated the landscape of the wrought industry because of their high performance capabilities at modest cost levels. Historically, chromium steels have had difficulty penetrating the powder metallurgy market because of oxidation issues. Recent powder manufacturing advances, however, have resulted in low-oxygen chromium steels such as Ancorsteel 4300, which enables the production of high performance parts with conventional processing techniques. The current work reviews the capabilities of this Cr-Si-Ni-Mo alloy and its derivatives. Static properties, dynamic properties, and dimensional stability data are reviewed with an emphasis on a sintering temperature of 1120 ºC (2050 ºF). Comparisons are made to traditional powder metallurgy materials in both the as-sintered and heat-treated conditions as well as to heat-treated wrought alloys.

189. Capabilities of Two Chromium Powder Metallurgy Steel for High Performance Applications at Conventional Sintering Temperatures Ancorsteel 4300, a high performance Cr-Si-Ni-Mo steel, was unveiled two years ago as the first in a series of powder metallurgy alloys that will simulate wrought steel compositions. Advantages of this alloy include good compressibility, high hardenability, and excellent dimensional stability. More important, however, is that this alloy has the ability to be effectively sintered at 1120 °C and maintain oxygen contents below 500 ppm. This unique blend of performance and processing capabilities provides static and dynamic properties that exceed those of conventional powder metallurgy alloys and approach wrought gearing materials. A second Cr-Si-Ni-Mo alloy has now been developed that offers complimentary performance levels at a lower Mo content. This manuscript reviews properties of the two chromium steels with comparisons to traditional sinter-hardened and heat-treated powder metallurgy alloys.

183. Performance Capabilities of High Strength Powder Metallurgy Chromium Steels with Two Different Molybdenum Contents The desire for advanced ferrous powder metallurgy materials has led to the development of alloys that simulate wrought steel compositions. A recently commercialized Cr-Si-Ni-Mo steel can be effectively sintered at conventional temperatures and provides good compressibility, high hardenability, and excellent dimensional stability while maintaining oxygen contents below 500 ppm. This alloy has demonstrated static and dynamic properties that exceed those of conventional powder metallurgy alloys and approach wrought gearing materials. A second Cr-Si-Ni-Mo alloy has now been developed to offer complimentary performance levels at a lower Mo content, while still providing excellent sinter-hardenability. The current work reviews static and dynamic properties of the two Cr steels with an emphasis on accelerated cooling rates after sintering at 1120 ºC (2050 ºF). Comparisons are made to traditional powder metallurgy materials processed in both the sinter-hardened and heat-treated conditions as well as to heat-treated wrought alloys.

178. Effects of Residual Surface Stress and Tempering on the Fatigue Behavior of Ancorsteel 4300 In this study, the microstructure, residual stress and fatigue behavior of Hoeganaes’ Ancorsteel 4300 sintered steel were characterized. Samples were tempered at either 205°C or 315°C and then machined by low-stress grinding. The effects of residual surface stress (measured by XRD) on the fatigue behavior were studied by either application of a stress-relieving heat-treatment after machining or by polishing away the machined surface. Based on this study, samples tempered at 315°C had slightly higher fatigue strengths than samples tempered at 205°C. Although significant compressive stresses were induced by machining on the surface of samples, these residual stresses did not affect the fatigue behavior. Rather, the fatigue behavior was controlled by porosity inherent to these sintered steels.

177. High Density Processing of Cr-Si-Ni-Mo Containing Steel Ancorsteel 4300, an iron alloy containing Cr-Si-Ni-Mo, was recently introduced and is capable of achieving high mechanical strength with exceptional dimensional stability. With the ability to be sintered at conventional temperatures, this alloy offers a unique blend of performance capabilities that can provide an economic advantage over alloy systems requiring high temperature sintering or secondary quench hardening. The current work discusses the performance of the new chromium steel at densities above 7.2 g/cm³at various cooling rates using an advanced lubricant/binder system. Comparisons to a hybrid Ni-Mo steel and a diffusion alloyed Ni-Cu-Mo steel are presented.

176. Sinter Hardening Response of a Cr-Si-Ni-Mo Containing Steel A number of sinter-hardenable materials have been developed over the past several years. Notable among these are Ancorsteel^®737 SH (prealloyed Mo, Mn, Ni steel), Ancorsteel 4600V (prealloyed Mo, Ni Steel) and hybrid alloys containing prealloyed molybdenum with copper and admixed nickel. All these materials use copper to enhance hardenability. Ancorsteel 4300 (Cr-Si-Ni-Mo containing steel) exhibits excellent hardenability without the addition of copper, with as-sintered hardnesses greater than 20 HRC utilizing cooling rates typically found in production sintering furnaces. A quantitative study to assess the hardenability of this alloy system has been undertaken and a comparison will be made with more traditional Mo-Ni-Cu alloys. Continuous sinter cooling transformation curves will be presented along with apparent hardnesses and metallographic analysis of various phase fractions.

167. High Performance Applications of Chromium Steels Sintered at Conventional Temperatures To meet the rigorous demands of automotive gearing, sprocket and other power transmission applications, double-press / double-sinter (DP/DS) techniques are often used to achieve the desired level of static and fatigue performance. Ancorsteel 4300, a new Cr-bearing material, has shown improved strength levels compared to traditional P/M steels. By employing such an alloy, core property requirements can be met at densities around 7.0 g/cm³. Replacing the pre-sinter and secondary press operations with selective densification, which will ensure sufficient contact fatigue resistance, can provide an economic benefit. The current work demonstrates the viability of processing a sprocket for a power transmission application with this high performance alloy system sintered at 1120 °C (2050 °F) in a production furnace. Subsequent selective densification and surface carburization provides a wear resistant and durable case layer. The results are compared with those achieved using FLN2-4405 processed through the traditional route of DP/DS, heat-treat.

166. A New CR-Bearing Alloy for High Performance Applications Ancorsteel 4300 was recently introduced to the marketplace and is the first in a series that will simulate wrought steel compositions. This new alloy represents a technological breakthrough with low sintered oxygen contents in a system that employs both chromium and silicon. Its main advantages include the ability to be effectively sintered at 1120 °C (2050 °F), good compressibility, high hardenability, and exceptional dimensional stability across a variety of processing conditions. These characteristics make this material an attractive cost-effective alternative to alloys that require secondary quench hardening treatments and enable the penetration of P/M into higher performance applications. The current work reviews the effects of density, cooling rate, and carbon content on the static and dynamic properties of this new product, along with comparisons to Q&T properties for wrought AISI grades 4340 and 8620.

165. High Density Processing of a New CR-Bearing Steel The application of P/M steels in highly stressed applications requires both high density processing and high performance alloys. Ancorsteel 4300, a new high performance alloy that contains Cr, Si, Mo, and Ni, utilizes the hardenability and mechanical property enhancement of chromium while maintaining low sintered oxygen contents. The elevated mechanical properties compliment the high compressibility of the powder allowing for use in high density applications. When combined with high density processing techniques such as the advanced lubricant/binder system AncorMax D, high densities and excellent properties can be achieved. This paper presents the effects of processing on density and mechanical properties with this new material, with a comparison to FLN2-4405 and FD-0405.

158. Chromium Containing Materials for High Strength-High Fatigue Applications As the use of P/M in advanced applications continues to grow, the industry continues to encounter increasing demands for high strength-high fatigue alloys. Ancorsteel 4300, a developmental alloy, has been engineered for high performance applications and employs the use of silicon, chromium, and molybdenum. This alloy will be the first in a new line of engineered high performance binder-treated products that simulate wrought steel compositions and can be processed at conventional sintering temperatures. Advanced fabrication techniques prevent the alloy from being susceptible to the common oxygen-related problems that are often seen with chromium-containing P/M materials. The presence of chromium and silicon with a low oxygen content serves to increase hardenability, strength, and fatigue life. This manuscript presents the effects of compaction pressure, cooling rate, and sintering temperature on the performance of the developmental alloy.

156. Development of a High Performance Nickel-Free PM Steel A developmental nickel-free P/M steel containing Cr, Mn, Si and Mo is being evaluated as a new high performance material. Bonded premixes with varying carbon contents were made with the AncorMax^®D system and pressed to densities of 7.2 g/cm³. Sintering studies were performed at 1177°C and 1260°C. Higher strengths were achieved in the CrMnSiMo steel as compared to a Ni containing steel with a higher total alloy content. Ultimate tensile strengths over 1200 MPa and hardnesses of 70 HRA can be achieved in the sinter + temper condition. The effect of sintering temperature, cooling profile and carbon content on mechanical properties and microstructure will be discussed.

143. Development of a High Performance Nickel-Free P/M Steel Chromium and manganese are used frequently in the wrought steel industry to improve mechanical properties and hardenability. However, these elements have been difficult to incorporate into P/M steels due to their high affinity for oxygen. A new nickel-free P/M steel containing Cr, Mn, Si and Mo is being developed for high performance applications. Sintering studies performed over a range of temperatures have shown that reasonable oxygen contents along with superior mechanical properties can be achieved with this new steel. The effect of sintering temperature and density on mechanical properties will be discussed.

142. Chromium Containing Materials for High Performance Components Recently developed silicon-bearing alloys were engineered to replace malleable and ductile cast irons, and have shown excellent property combinations at high sintering temperatures. A modification to these alloys merges the power of silicon and chromium in one system, and allows for extraordinary performance. The presence of chromium improves both static and dynamic properties with the added benefit of being close to die-size after sintering. The current work details extensive laboratory data that show the effects of compaction pressure on this modified alloy processed at high sintering temperatures. Also presented is a field experience on a heat-treated production component that combined the high performance alloy system with warm compaction technology. Static and dynamic properties are presented for samples sintered in both laboratory and production scale furnaces.

141. Effects of Cooling Rate on the Hardenability of Chromium Containing P/M Steels Two chromium containing grades, Cr-modified Ancorloy^®MDC and a developmental CrMnSiMo steel, have been investigated to develop an understanding of the phase transformation behavior of these steels during cooling. The cooling rates studied are in the range typically found in sintering furnaces. A quantitative study to assess the hardenability of these materials has been undertaken and the results of dilatometric, metallographic and hardness evaluations to determine the effects of cooling rate on the various Cr containing steels are presented.

128. Chromium Additions to the Ancorloy MD Series Ancorsteel 41AB, introduced several years back, demonstrated the benefits of chromium and manganese additions to molybdenum steels. The more recently developed Ancorloy MD series provides enhanced ductility and strengths in P/M steels. This paper examines the mechanical properties achieved through the combination of high performance materials with chromium additions and high temperature sintering. Two chromium-modified materials were developed by replacing a portion of admixed nickel with a high carbon ferroalloy to improve dimensional properties and hardenability. Reviews of properties such as tensile, impact, transverse rupture, rotating bending fatigue, hardenability, and compressibility are presented.

124. Properties and Applications of High Density Sinter-Hardening Materials Sinter-hardening materials are characterized by their high hardenability which enables the formation of >80% martensite during accelerated cooling. However, these moderately alloyed materials often exhibit lower compressibility and the resulting lower density limits their use in potential high strength applications.

What is needed is a method to improve the green and sintered density of current sinter-hardening materials that will enable these materials to be utilized in new high strength applications. This paper describes how the green and sintered density of standard sinter-hardening alloys can be improved using new alloy systems coupled with advanced binder technology. The resulting improvements in mechanical properties will be presented as well as the potential use of high density

68. Performance Characteristics of a New Water-Atomized Prealloyed Powder (0.5 weight % Molybdenum A new prealloy material containing 0.50 w/o Mo was introduced recently. This medium hardenability material can be admixed with a variety of alloying ingredients to produce superior tensile properties. Results of admixing this prealloyed powder with nickel, copper, manganese, and graphite will be presented. In addition, quench and temper properties will also be discussed.

60. Application of High Performance Materials and Processes - Alloy Systems Significant advances have been made in the past several years in developing Low alloy materials for highly stressed applications. A review of these material and processing developments will be made. Recent material developments focus on developing high apparent hardness and tensile strength in P/M parts without the need for a secondary quench-hardening operation. The effect of alloy type, alloy content, and cooling rate on hardness and other properties will be discussed.

42. The Effect of Microstructure on Fatigue Properties of High Density Ferrous Materials Fatigue testing (rotating bending fatigue) has been performed on several high performance ferrous P/M material systems. Detailed metallographic analysis was performed to determine differences in the failure mechanisms for various material and process combinations. A variety of material compositions were single compacted to high density via the ANCORDENSE™ compaction system. This was followed by conventional and high temperature sintering and testing in the as-sintered and heat treated conditions. The analysis provides information as to the relationships between density, structure and composition with fatigue life.

38. Powder Metallurgy Gears - Expanding Opportunities Powder metallurgy (P/M) is a precision metal forming technology for the manufacturing of parts to net, or near net shape. The powder metallurgy process is illustrated schematically in Figure 11. There are three basic steps to producing parts; mixing, compacting, and sintering. Variations to these basic steps such as infiltration, double pressing/double sintering, and powder forging may be used to achieve higher density parts. A sizing operation may be used to qualify critical part dimensions. Alternatively, a machining step may be added for the same purpose or to achieve a geometric feature not possible during rigid die compaction. P/M parts may be through hardened or surface hardened as required by the intended application.

31. Advanced Properties of High Density Ferrous Powder Metallurgy Materials The introduction of the ANCORDENSE™ system has provided significantly higher density levels than previously possible in a single press/single sinter operation. This paper will explore the role that higher density has on mechanical properties. Various properties will be evaluated, including transverse rupture strength, tensile strength, and impact. Additionally, the effect of other processes, such as high temperature sintering and heat treatment, will be addressed.

27. Recent Developments in Ferrous Powder Metallurgy Alloys A systems approach to engineered ferrous powder metallurgy (P/M) materials is described. The approach encompasses the use of high compressible, high performance powders in premixes produced using proprietary mixing technology that employs patented binders. To ensure that an appropriate microstructure is achieved to suit the functional requirements of a particular application, alloys are formulated based on knowledge of the compaction and sintering cycle that will be used to make the P/M parts. These premixes have improved flow and die filling characteristics that result in greater consistency throughout the entire P/M part manufacturing process. In addition, the use of binder treated premixes leads to reduced dusting and segregation of alloy additions. Binder treated premixes produced using high compressible, prealloyed molybdenum steel powders are shown to be particularly well suited for quench-hardening, sinter-hardening, and high temperature sintering. They also form the basis for a series of chromium, manganese, and chrome-manganese P/M 'Steels. The systems approach will be augmented during 1994 by the introduction of new material and process technology that enables part densities of 7.3 to 7.5 g/cm3 to be achieved through single compaction processing.

22. High Density Processing of CR-Mn P/M Steels The use of chromium and manganese as alloying elements in P/M steels offers several potential advantages over copper and nickel that are used in conventional P/M alloy steels. The paper will illustrate how the principles used to improve the hardenability and performance of wrought steels can be applied to P/M chromium and manganese alloy steels using a systems approach. The use of chromium-manganese for P/M applications was made possible by binder-treated premix technology of a highly compressible prealloyed low alloy base material. The flexibility of alloy design will be illustrated by examples of through hardening, high strength low alloy steels.

15. Surface-Hardenable Heat Treated P/M Steels The addition of fine particles (< 20µm) of high-carbon ferroalloys to the high compressible prealloy powders, Ancorsteel® 85 HP and Ancorsteel 150 HP, has been shown to be a practical way of producing ferrous low-alloy steels containing chromium and manganese. Increased sintering temperatures improved the mechanical properties of the materials and the effect was particularly noticeable at 2350°F.

The ferroalloy additions significantly enhanced the hardenability of the base low-alloys. Materials based on the low-alloy powder containing 1.5% molybdenum were more hardenable than those based on the 0.85% molybdenum alloy. These materials are well suited for plasma nitriding and should find use in gears and cams that require a hard wear-resistant surface coupled with a strong, tough core.

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